Virally-encoded neuraminidase plays a key role in the life-cycle of the influenza virus. A class of anti-influenza drugs that inhibits the action of neuraminidase has garnered increasing interest in the pharmaceutical industry due to their selectivity and potency. The inhibitors are transition state analogs of the enzyme substrate, sialic acid, and are highly efficacious in in vitro and in vivo studies, with IC50 values in the nM range. However these drugs are very polar and consequently have poor oral bioavailability. At TSRL, we have a developed an amino acid prodrug strategy that targets intestinal transporters for enhanced uptake. Subsequent activation of the absorbed prodrug can then occur either through targeted enzymatic hydrolysis of the prodrug or chemical breakdown of the prodrug to the activate parent compound. This strategy is based on a molecular mechanistic understanding of the transport and activation pathways in cells and tissues and the interaction of prodrug structures with these pathways. In this proposal, we have developed novel amino acid prodrugs of two neuraminidase inhibitors and provide strong supporting data showing that these prodrugs are actively transported by intestinal transporter and are well absorbed. We show that through our approach, we can boost the oral availability of selected neuraminidase inhibitors to an extent that they are effective in animal models of influenza and have high potential to be developed as oral drug products. In the current project, we propose to select a lead neuraminidase inhibitor by in vivo (mouse and ferret) testing of the developed series of compounds against a range of influenza strains, including recent H1N1 isolates, seasonal flu isolates, drug resistant virus and high pathogenic strains of the virus. Our molecular mechanistic approach to prodrug design has enormous potential for the development of orally effective neuraminidase inhibitors.